Abstract: A number of metals including Fe(II)/Fe(III), Al(III), Zn(II) and Cu(II) are found co-localised with β-sheets of Aβ42 in senile plaque cores in AD brain. We know neither why nor how the co-localisation takes place or, indeed, if it is entirely aberrant or partly protective. There are data from in vitro studies which may begin to explain some of these unanswered questions and in considering these I have summised that Al(III) and Fe(III)/Fe(II) are directly involved in the precipitation of β-sheets of Aβ42 in senile plaque cores whereas the presence of Cu(II) and Zn(II) is adventitious. The co-deposition of Al(III), Fe(III) and β-sheets of Aβ42 could act as a source of reactive oxygen species and begin to explain some of the oxidative damage found in the immediate vicinity of senile plaques. Whether such metal-Aβ42 synergisms are an integral part of the aetiology of AD remains to be confirmed.